diff --git a/lib/session-file-store.js b/lib/session-file-store.js
index fe0cfdb184..90be2bc871 100644
--- a/lib/session-file-store.js
+++ b/lib/session-file-store.js
@@ -11,12 +11,11 @@ class FileStore extends Store {
   }
 
   async set (sessionId, session, callback = noop) {
-    let storedSessionId
     try {
       // Delete any expired sessions before creating a new session
       const storedSessionFiles = await fse.readdir(this.path)
       await Promise.all(storedSessionFiles.map(async sessionFile => {
-        storedSessionId = sessionFile.replace('.json', '')
+        const storedSessionId = sessionFile.replace('.json', '')
         try {
           const storedSession = await fse.readJson(path.join(this.path, sessionFile))
           if (isExpired(storedSession)) {